241Driven plate lining face inspection

Driven plate friction facings should, after a short period of service, give a polished appearance due to the frequent interface rubbing effect. This smooth and polished condition will provide the greatest friction grip, but it must not be confused with a glazed surface created by the formation of films of grease or oil worked into the rubbing surfaces, heated and oxidized.

A correctly bedded-in friction facing will appear highly polished through which the grain of the friction material can be clearly seen. When in perfect condition, these polished facings are of a grey or mid-brown colour. A very small amount of lubricant on the facings will burn off due to the generated heat. This will only slightly darken the facings, but providing polished facings remain so that the grain of the material can be clearly distinguished, it does not reduce its effectiveness.

Large amounts of lubricant gaining access to the friction surfaces may result in the following:

a) The burning of the grease or oil may leave a carbon deposit and a high glaze, this hides the grain of the material and is likely to cause clutch slip.

b) If the grease or oil is only partially burnt and leaves a resinous deposit on the facings it may result in a fierce clutch and may in addition produce clutch spin caused by the rubbing interfaces sticking.

c) If both carbon and resinous deposits are formed on the linings, clutch judder may develop during clutch take-up.

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